Process for Treating Sludge and Manufacturing Bioorganically-Augmented High Nitrogen-Containing Inorganic Fertilizer

ABSTRACT

The invention describes a new method for treating sludge, which can result in the production of high nitrogen organically-augmented inorganic fertilizer that incorporates municipal sludges or biosolids or organic sludges that can compete with traditional fertilizers such as ammonium phosphate, ammonium sulfate and urea on the commodity fertilizer marketplace. The method takes advantage of the thixotropic property of dewatered biosolids or organic sludge to create a pumpable paste-like material from the biosolids or organic sludge that is then treated with an oxidizer to reduce odorant effects and an acid. This mix is then interacted with concentrated sulfuric and or phosphoric acids and an ammonia source or alternatively a hot or molten melt or salt of ammonium sulfate/phosphate to form a fertilizer mix. The present invention controls the heat, atmospheric pressure and retention time of the fertilizer mix in the reaction vessel. When a fertilizer melt is formed ammoniation is subsequently completed by the specific use of vaporized ammonia. The invention can also be an add-on to commercial production of ammonium salts. The fertilizer produced by the present invention contains more than 8 wt. % nitrogen and preferably 15 wt. % nitrogen. The invention is oriented to be tailored to the biosolids production for individual municipal waste treatment plants in order to keep the fertilizer manufacturing plants of the present invention small with a minimization of logistics and liability.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.60/890,422, filed Feb. 16, 2007, entitled “Process for Treating Sludgeand Manufacturing Bioorganically-Augmented High Nitrogen-ContainingInorganic Fertilizer,” which is specifically and entirely incorporatedby reference.

BACKGROUND

1. Field of the Invention

This invention is directed to systems, devices, and methods for thetreatment of sludge, and preferably, to systems, devices, and methodsfor manufacturing fertilizers, more preferably a bioorganic-augmentedhigh nitrogen-containing inorganic ammonium fertilizer utilizingprimarily organic sludges including municipal dewatered sludges orbiosolids, concentrated acids and ammonia. The invention is alsodirected to products produced by processes of the invention.

2. Description of the Background

The disposal of sludges discharged from municipal wastewater treatmentplants is a serious and growing problem. In 1990, the United StatesEnvironmental Protection Agency indicated that a family of fourdischarged 300 to 400 gallons of wastewater per day and in 2000 thisnumber has almost doubled. From this wastewater, publicly ownedtreatment works generate approximately 7.7 million dry metric tons ofsludge (or “biosolids” as these municipal sludges are now called)annually or about 64 dry pounds of sludge for every individual in theUnited States.

The definitions of “sewage sludge” and “sludge” and “biosolids” underTitle 40 of the Code of Federal Regulations, Part 257.2, herebyincorporated by reference, is as follows:

-   -   “Sewage sludge means solid, semi-solid, or liquid residue        generated during the treatment of domestic sewage in a treatment        works. Sewage sludge includes, but is not limited to, domestic        septage; scum or solid removed in primary, secondary or advanced        wastewater treatment processes; and a material derived from        sewage sludge. Sewage sludge does not include ash generated        during the firing of sewage sludge in a sewage sludge        incinerator or grit and screenings generated during preliminary        treatment of domestic sewage in a treatment works. Sludge means        solid, semi-solid or liquid waste generated from municipal,        commercial, or industrial wastewater treatment plant, water        supply treatment plant, or air pollution control facility or any        other such waste having similar characteristics and effect.”

For the purposes of the present application, the term sludge alsoencompasses municipal dewatered biosolids, domestic septage, heat-driedbiosolids, pharmaceutical fermentation wastes, microbial digests oforganic products such as food stuffs, food byproducts, animal manures,digested animal manures, organic sludges comprised primarily ofmicroorganisms, and any combination thereof.

There are several types of sludges that can be produced from sewageand/or wastewater treatment. These include primary sludge, wasteactivated sludge, pasteurized sludge, heat-treated sludge, andaerobically or anaerobically digested sludge, and combinations thereof.These sludges may be from municipal and/or industrial sources. Thus,sludges can comprise macromolecules including proteins. Sludges cancomprise personal pharmaceutical compounds, antibiotics, hormones,hormone-like molecules, other biologically active compounds, andmacromolecules including proteins. Thus, an urgent need exists for aneffective, efficient, and economical process for treating sludges.

Commonly, but inadequately, sludges are merely dewatered to the bestextent possible by chemical and mechanical means. The water content ofsewage sludges is still very high, and none of the undesirable compoundslisted above are neutralized. Typical sludges coming out of a gravityclarifier may have a dry solids content of 2% or less. After anaerobicdigestion, the solids content can be about 10%. Cationic water-solublepolymers have been found useful for causing further separation betweenthe solids and the water that is chemically and physically bound.Filtration or centrifugation of cationic polymer treated sludgetypically yields a paste-like sludge cake containing a range of solids,commonly from 18% to 30% solids.

Drying of sewage sludge (to greater than 90% solids) has been practicedfor many years in both the United States and Europe. Sludge drying inthe United States prior to about 1965 was undertaken to reducetransportation costs and in pursuit of various disposal options. In someplants, the sludge was dried in powder form and the fine particles wereconsumed in the combustion chamber of an incinerator or boiler. In thelate 1960's two municipalities, Houston and Milwaukee, began to market apelletized or granulated dried sludge for use as a soil amendment and/orfertilizer. Several more plants for manufacture of dried pelletizedsludge were built in the 1980's and 1990's; especially after oceandumping of sludge by coastal cities was eliminated. Drying andconversion to a heat-dried biosolids pellet fertilizer was the bestoption for these metropolitan areas where landfills and land fordisposal were limited and even in 2007 it remains a very viabletechnology. However, the investment required for a sludge dryingfacility is very large resulting in municipal costs greater than $300per dry ton of biosolids, and in many cases greater than $500 per dryton of biosolids.

The most common type of sludge dried and pelletized isanaerobically-digested municipal sewage. Anaerobic digestion, as thename suggests, involves treatment by facultative bacteria underanaerobic conditions to decompose the organic matter in the sludge.After a prescribed time and temperature, a sludge relatively free ofputrifiable organic matter is obtained. Unfortunately, some pathogensremain in such biosolids, and the USEPA has classed such treatedbiosolids as Class B implying that they are of a lower standard than the“Class A” treated biosolids. Because Class B biosolids contain pathogenindicators—and therefore potential pathogens, they are restricted in themanner by which they can be applied to animal and human crops. Incontrast, Class A biosolids, e.g., heat-dried biosolids pellets, as wellas the product of the present invention, are not restricted undercurrent USEPA standards as fertilizer for animal or human crop usage.

If pathogens (e.g. Salmonella sp. Bacteria, enteric viruses, and viablehelminth ova) are below detectable levels, the biosolids meet the ClassA designation. The Part 503 rule (Title 40 of the Code of FederalRegulations, Part 503, incorporated herein by reference] lists sixalternatives for treating biosolids so they can be classified in Class Awith respect to pathogens. Alternative 1 requires biosolids to besubjected to one of four time-temperature regimes. Alternative 2requires that biosolids meet pH, temperature and air-dryingrequirements. Alternative 3 requires that when biosolids are treated inother processes, it must be demonstrated that the process can reduceenteric viruses and viable helminth ova, and operating conditions usedin the demonstration after pathogen reduction demonstration is completedmust be maintained. Alternative 4 requires that when biosolids aretreated in unknown processes, biosolids be tested for pathogens at thetime the biosolids are used or disposed or, in certain situations,prepared for use or disposal. Alternative 5 requires that biosolids betreated in one of the Processes to Further Reduce Pathogens. Alternative6 requires that biosolids be treated in a process equivalent to one ofthe Processes to Further Reduce Pathogens, as determined by thepermitting authority.

Class A pathogen biosolids must also possess a density of fecal coliformof less than 1,000 most probable numbers (MPN) per gram total solids(dry-weight basis) or a density of Salmonella sp. Bacteria of less than3 MPN per 4 grams of total solids (dry-weight basis). Either of thesetwo requirements must be met at one of the following times: when thebiosolids are used or disposed; when the biosolids are prepared for saleor give-away in a bag or other container for land application; or whenthe biosolids or derived materials are prepared to meet the requirementsfor Exceptional Quality biosolids.

All biosolids applied to the land must meet the ceiling concentrationfor pollutants, comprising 10 heavy metal pollutants: arsenic, cadmium,chromium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc.If a limit for any one of these is exceeded, the biosolids cannot beapplied to the land without the incorporation of significantrestrictions. Exceptional Quality (EQ) is a term used by the USEPA Guideto Part 503 Rule 7 to characterize biosolids that meet low-pollutant andClass A pathogen reduction (virtual absence of pathogens) limits andthat have a reduced level of degradable compounds that attract vectors.It is the intent of this invention that all biosolids meet or exceed theUSEPA's Exceptional Quality (“EQ”) standard for metal levels.

Pathogen reduction must take place before or at the same time as vectorattraction reduction, except when the pH adjustment, percent solidsvector attraction, injection, or incorporation options are met. Finally,vector attraction reduction must be met when biosolids are applied toland. Most commonly, this will be achieved by drying the biosolidsproduct to a level of greater than 90% solids.

Sludge that is merely dried, as with heat-dried pellets, even if driedto greater than 90% solids, has several disadvantages for agriculturaluse. It has low fertilization value, typically having nitrogen contentof only about 2-5%. Freight and application costs per unit of nitrogenare high. The heat-dried biosolids often has a disagreeable odor,particularly when moist. Also, dried pellets have low density andhardness and when blended with other commercial fertilizer materials,the pellets may segregate, and disintegrate and may not spread on thefield uniformly with other more dense ingredients. Some bacterial actionmay continue when the material becomes moist, and under storageconditions, the material's temperature may rise to the point ofautoignition. Hence, except for special markets that value its organiccontent for soil amendment or filler in blended fertilizer, there isrelatively poor demand for the heat-dried biosolids product. In mostcases municipalities must pay freight charges, or may offer otherincentives for commercial growers to use the material. However, this isfrequently still more economical than alternative disposal schemes.

The market value for agricultural fertilizers is principally based ontheir nitrogen content. A need exists for a practical, safe and economicmethod for increasing the nitrogen content of biosolids to a levelapproaching that of commercial mineral fertilizers, i.e., 10-20%. Ifsuch a biosolids fertilizer could be manufactured then overall value ofthe biosolids product and demand for the product would increase.Moreover, a properly manufactured biosolids fertilizer will have anadvantage in that much of its nitrogen will be of the slow release type.This is very desirable since it provides nitrogen to the plant allthrough its growing cycle. Traditional inorganic manufactured slowrelease nitrogen fertilizers have a price many times that of ordinarymineral nitrogen fertilizers. Under the scenario of high nitrogenbiosolids-containing fertilizer production from their biosolids,municipalities would enjoy public and regulatory support for theirbiosolids disposition program. Such a program would ensure the regularremoval of their dewatered or dried biosolids, by, for example,recycling biosolids into a high nitrogen fertilizer which then can besold directly into the mature national fertilizer distribution industry,thereby eliminating one of the major problems traditionally associatedwith biosolids treatment programs.

Prior attempts have been made to reach some of these objectives. U.S.Pat. Nos. 3,942,970, 3,655,395, 3,939,280, 4,304,588, and 4,519,831describe processes for converting sewage sludge to fertilizer. In eachof these processes a urea-formaldehyde condensation product is formed insitu with the sludge. Thus, the processes require the handling offormaldehyde, a highly toxic lachrymator and cancer suspect agent.

Other processes require costly process equipment and/or specialconditions not readily incorporated in existing sewage treatmentfacilities (See: Japanese Patent No. 58032638; French Patent No.2,757,504).

A simple method for increasing the nitrogen in sludge would be to blendcommercial nitrogen fertilizer materials to the wet sludge prior todrying and pelletizing. There are only a few high-nitrogen fertilizermaterials that are economical for use in agriculture. Examples are:ammonia (82 wt. % N), urea (46 wt. % N), ammonium nitrate (35 wt. % N).Ammonia has high volatility and is subject to strict regulation ofdischarges to the atmosphere. Urea is a solid that adsorbs moisturequite readily and makes the sludge more difficult to dry. Urea is alsohighly susceptible to breakdown to ammonia by the microbes and enzymesin biosolids if they are not properly prepared, resulting in nitrogenloss and an odor problem Ammonium nitrate is a strong oxidizer and canresult in a potential explosion problem which has all but eliminatedthis fertilizer from the commercial market after 2000. All of thesefertilizers have high nitrogen content, but are less than ideal forcombining with biosolids absent special processing.

Other references, such as European Patent No. 0143392 B1, JapanesePatent No. 9110570 A2, and “Granulation of Compost From Sewage Sludge.V. Reduction of Ammonia Emission From Drying Process”, HokkaidoritsuKogyo Shikenjo Hokoku, 287, 85-89 (1988)) fail to disclose the use ofacids with ammonium sulfate additions and do not discuss the issue ofcorrosion of steel process equipment under acid conditions.

Over the past thirty years alkaline stabilization of biosolids has beena standard and successful method of making biosolids into beneficiallyuseful materials that can be used principally as soil-conditioningmaterials. Because these alkaline-stabilized biosolids products havehigh calcium carbonate equivalencies, they have been produced andmarketed as AG-lime materials, usually as a replacement for calciumcarbonate in farm soil management strategies. Because of this usage, thevalue of these materials has been restricted to only a few dollars perton of product; therefore, because of transportation costs especiallysince they usually contain significant water concentrations—often up to50%—they are economically and geographically restricted to areas closeto the source of their treatment.

Thus, there is a long standing need for practical means of increasingthe economic value of sewage sludge through increasing its nitrogencontent, and increasing its ability to be spread as well as a need totreat these materials such that they are converted into commodityfertilizers with physical and chemical and nutrient properties such thatthey can command significant value in the national and internationalcommodity fertilizer marketplace. A series of U.S. patents, U.S. Pat.Nos. 5,984,992; 6,159,263; 6,758,879 and No. 7,128,880 have described amethod of production of high nitrogen organically enhanced ammoniumsulfate fertilizers made with biosolids utilizing a pipe-cross reactoras originated by the Tennessee Valley Authority. The pipe, tee andpipe-cross reactor are defined by the IFDC in the Fertilizer Manual(1998), p 440 as:

-   -   “the pipe reactor consists basically of a length of        corrosion-resistant pipe (about 5-15 m long) to which phosphoric        acid, ammonia and often water are simultaneously added to one        end through a piping configuration resembling a tee, thus the        name “tee reactor.” . . . . The tee reactor was modified by TVA        to also accept an additional flow of sulfuric acid through        another pipe inlet located opposite the phosphoric acid inlet,        giving the unit a “cross” configuration and thus the name        “pipe-cross reactor”.

Both the IFDC Fertilizer Manual (1998) and the Fertilizer Technical DataBook (2000) refer to the pipe-cross reactors. It was thought that pipecross reactors delivered a more concentrated mix to the granulatorshaping device and more efficiently evaporated undesired water from thefertilizer mix than other devices, but these references demonstrate along-felt need for improvement, indicating that one of the shortcomingsof the pipe cross reactor is scale formation inside the pipe which canresult in clogging.

The methodologies taught by this group of patents (U.S. Pat. Nos.5,984,992; 6,159,263; 6,758,879 and No. 7,128,880) are plagued byproblems related to the blockage of these narrow relative to theirlength reaction “pipe-like” reactor configurations during operation andrelated to the difficulty of control of the reaction temperature andpressure and retention time of the mix within such pipe-cross reactors.These pipe-cross reactors are narrow in contrast to their length, e.g.,up to 6 to 8 inches in diameter and often 15 feet in length or longer.The plant practicing the manufacture of organically-enhanced ammoniumsulfate fertilizers often had to shut down and disassemble thepipe-cross reactor either due to blockage from biosolids buildup or fromdestructive over heating in such reactors such that the commonly used“Teflon” coating on the interior-reaction side of the reactor was meltedand ruined. Further, the use of the pipe-cross reactor has the distinctdisadvantage of having very short reactor retention times (usually lessthan 20 seconds) which is an advantage in the manufacture of traditionalfertilizers like ammonium sulfate but is a disadvantage when coupled tothe simultaneous process of biosolids. Such short processing timeincreases the probability of untreated or non-homogenous mixing as thethree material inputs pass through this reactor. Also limiting is thelack of control over the atmospheric pressure within such pipe-crossreactors since these reactors have open ended discharges usuallydirectly into a granulator.

U.S. Pat. No. 4,743,287 issued in 1988 by Robinson described a method touse two reaction vessels in sequence to incorporate organic sludges intonitrogen fertilizers of low or medium nitrogen concentration (a range of4 wt. % N to a maximum of nitrogen concentration of 10 wt. %). Robinsonuses his first reaction vessel to achieve very low pH values of themixture (pH 0.2 to 1.5) to achieve hydrolysis of some molecules presentand to prepare the mix for reaction in a second reaction vessel.Robinson does teach that a single reactor can be used but only in abatch configuration and not in a continuous flow manufacturing method.In all cases, Robinson teaches that the acid and ammonia may be injectedin either order but must be injected in sequence. This patentimportantly describes the reaction vessels capable of achieving highpressures (30 PSI) with relatively long retention times as compared tothe pipe-cross reactors. However, Robinson fails to meet the need for anovel and practical continuous flow method of manufacturing highnitrogen (greater than 8% wt. % N) and biosolids-containing fertilizerproducts under the advantages of defined temperatures, pressures andreaction retention times.

SUMMARY OF THE INVENTION

Embodiments of the present invention overcome the problems anddisadvantages associated with other systems and methods for treatingbiosolids or sludges and for manufacturing fertilizers from sludges andrelated waste materials. Note the term “biosolids” is now commonly usedto describe sludges as produced at municipal wastewater treatmentplants. Other embodiments of the present invention overcome the problemsand disadvantages inherent in the fertilizers prepared by other systemsand methods.

Embodiments of the invention can convert potentially hazardous sludgeinto bioorganic-augmented inorganic fertilizers without the need fortraditional massive fertilizer manufacturing facilities that arecommonly multiple stories tall or higher. Unlike the art as practiced byU.S. Pat. Nos. 5,984,992; 6,159,263; 6,758,879 and 7,128,880,embodiments of the present invention can be scaled to match thedewatered biosolids production of individual or specific municipalwastewater treatment plants (102) or the collective wastewater treatmentplants of a single municipality. Because of this, the fertilizerproduction process of the present invention can be sited directlyadjacent to or near to municipal wastewater treatment plant facilitiesthereby eliminating the need for transport of the biosolids to distantfertilizer manufacturing facilities. This location of a manufacturingfacility adjacent or close to the wastewater treatment plant drasticallyreduces the logistics and liability, e.g., costs and hazards involved intransporting sludge to the fertilizer manufacturing facility.

One embodiment of the invention is directed to treating a sludge,especially as dewatered sludge ranging between 14% and 40% solids, byfirst conditioning the sludge. The step of conditioning the sludge caninclude, but is not limited to making the sludge pumpable by takingadvantage of the thixotropic property of the sludge by mixing the sludgewith a force sufficient to make it pumpable thereby creating a morehomogenous paste-like mix or by adding a liquid, such as blowdownacid-water from a scrubber system. This mix is further conditioned withthe addition of one or more oxidants, preferably calcium ferrate, toreact with odorants present in the sludge such as reduced sulfurcompounds. In an optimal embodiment, this mix is further conditionedwith the addition of specifically phosphoric acid to continue thetreatment of odorants as well as enhance the granulation of the granulesas well as the nutrient value of the finished fertilizer. Theconditioned sludge is then added to a pressure vessel. One or more acidsand one or more nitrogen sources are combined in a reaction zone locatedwithin the conditioned sludge. As defined in greater detail later, thereaction zone is an area of optimal application of any acid, any base,any nitrogen source, and any combination thereof, in order for thesludge to be treated in embodiments of this invention. At least one ofthe one or more nitrogen sources comprises a base, and so an exothermicreaction can take place between the acid and the base. Subsequently,this mix is maintained in a stress condition for a retention period.

Similar results are obtained by another embodiment of the inventionwhich is directed to treating a sludge by first conditioning the sludge.The step of conditioning the sludge can include, but is not limited tomaking the sludge pumpable by mixing the sludge with a force sufficientto make it pumpable or by adding a liquid, such as blowdown acid-waterfrom a scrubber system. The conditioned sludge may be furtherconditioned by the addition of an oxidant and phosphoric acid. Theconditioned sludge is then added to a pressure vessel. In thisembodiment, one or more acids, one or more nitrogen sources, and one ormore bases are combined in a reaction zone located within theconditioned sludge. An exothermic reaction can take place between theacid and the base. Subsequently, this mix is maintained in a stresscondition for a retention period.

Similar results are obtained by another embodiment of the inventionwhich is directed to treating a sludge by first conditioning the sludge.The step of conditioning the sludge can include, but is not limited tomaking the sludge pump able by mixing the sludge with a force sufficientto make it pumpable or by adding a liquid, such as blowdown acid-waterfrom a scrubber system. The conditioned sludge may be furtherconditioned by the addition of one or more oxidants, preferably calciumferrate and subsequently by phosphoric acid. The conditioned sludge isthen in sequence mixed with a concentrated acid, preferably sulfuricacid prior to being added to a pressure vessel. In this embodiment, oneor more nitrogen sources, and one or more bases are combined in areaction zone located within the acidified conditioned sludge. Anexothermic reaction can take place between the acid and the base.Subsequently, this mix is maintained in a stress condition for aretention period.

Similar results are also obtained by another embodiment of theinvention, which is directed to treating a sludge by first conditioningthe sludge. The step of conditioning the sludge can include, but is notlimited to making the sludge pumpable by mixing the sludge with a forcesufficient to make it pumpable or by adding a liquid, such as blowdownacid-water from a scrubber system. Further, the sludge can beconditioned by the reaction with one or more oxidants and the additionof phosphoric acid. The conditioned sludge is then added to a pressurevessel. In this embodiment, a reactive mixture is added to theconditioned sludge. The reactive mixture is typically a hot melt and/orsalt of ammonium sulfate and/or ammonium phosphate. Subsequently, thismix is maintained in a stress condition for a retention period.

In all of these embodiments, the stress condition can optionally resultin the partial hydrolysis and/or denaturation of any macromoleculesincluding proteins contained in the sludge component of the mix. Thestress condition can also optionally result in the partial hydrolysisand/or denaturation of any personal pharmaceutical compounds,antibiotics, hormones, hormone-like molecules, or other biologicallyactive compounds.

Other embodiments of the present invention continue the treatment ofsludge until safe, sterile fertilizers are produced. These fertilizerscan actually exceed the requirements of a USEPA Class Abiosolids-containing product. The fertilizer products produced are ofsuitable dryness, hardness and chemical quality to produce a valuable,high-nitrogen, commercial fertilizer product that is capable ofcompeting in an international marketplace against other inorganicfertilizers. Further, the fertilizer products typically contain ammoniumnitrogen bound to compounds, especially organic compounds, in the mixsuch that the nitrogen dissolves slowly and migrates slowly through thetop 8 inches of soil which is the critical zone for nutrient uptake bycrops planted on said soil. This dissolution and migration is muchslower than that observed if the ammonium ions are not attached toorganic compounds such as occurs when traditional inorganic fertilizers,e.g., the salt, ammonium sulfate, are directly applied to the soil.

Other embodiments and advantages of the invention are set forth in partin the description, which follows, and in part, may be obvious from thisdescription, or may be learned from the practice of the invention.

DESCRIPTION OF THE FIGURES

FIG. 1. Summary overview of the relationship of the present invention toa community.

FIG. 2. Schematic overview of the fertilizer production Ammonium Mix(“AM”) process using thixotropic biosolids and inorganic acids andammonia to produce a high nitrogen containing organically-augmentedinorganic ammonium fertilizer.

FIG. 3. Detailed schematic of the fertilizer production process of thepresent invention.

FIG. 4. Detailed schematic of the fertilizer manufacturing process ofthe present invention utilizing a single pressure vessel, receivingseparately but simultaneously conditioned biosolids, concentrated acidand an ammonia source, that controls the internal temperature,atmospheric pressure, and retention time of the treated mix. Furtherthis figure shows that the mix created in the pressure vessel isdischarged to a pugmill for completion of the ammoniation usingvaporized ammonia, addition of hardening agents and addition of recycle.This pugmill begins the shaping process for the mix prior to itsentering the granulator.

FIG. 5. Detailed schematic of the fertilizer manufacturing process ofthe present invention utilizing two pugmills in the conditioningprocess. The first pugmill is used to prepare the biosolids byaggressive mixing, adding an oxidant or oxidants. In this example thephosphoric acid is added to the pressure vessel. The second pugmill isused to add, in this example, all of the aqueous ammonia used as thebase in the exothermic reaction that will occur in the pressure vessel.The pressure vessel receives separately but simultaneously the highlyammoniated conditioned biosolids and a concentrated acid source. Thereaction in the pressure vessel is used to control the internaltemperature, atmospheric pressure, and retention time of the treatedmix.

FIG. 6. Schematic view of an embodiment of the pressure vessel used inthe Ammonium Mix or “AM” and Pellet Beneficiation or “PB” processes. Thehydrolysis or pressure vessel is used to create a mix of organic sludgewith ammonium sulfate and ammonium phosphate using concentrated acid andan ammonia source, preferably anhydrous ammonia injected separately butsimultaneously with the acid and the sludge. This vessel receivesconditioned mix at an opening in the bottom of the vessel. Just aboveand injected simultaneously are the inputs of concentrated acid andmultiple inlets, commonly four, for an ammonia source, preferablyanhydrous ammonia. The fertilizer mix created rises up through thevessel under controlled temperature and atmospheric pressureenvironments which facilitate sterilization, hydrolysis and ordenaturation of macromolecules in the fertilizer mix and drying due torelease of steam and water vapor at the top of the vessel. The preferredvessel is agitated to maintain constant conditions and to facilitateremoval of the fertilizer mix. The vessel also has a significant headspace at the top of the vessel to facilitate steam withdrawal and topermit input of pressurized air for use when the pressure vessel must beemptied for maintenance or process shutdown. The pressure vessel in thisfigure also contains preferably a protective coating in the inside ofthe vessel, e.g., Havey or Kynar coatings, to protect the wall ofpressure vessel from the aggressive effects of the concentrated acid andthe acid-base reaction. The pressure vessel may contain, alternatively,a layer of acid brick and of carbon brick to protect the lower shell ofthe vessel from these harsh conditions.

FIG. 7. Schematic view of the return loop system for permittingmaintenance or shutdown of the first pugmill and the pressure vessel inthe AM and PB processes. This schematic shows the positioning of valvesand return lines permitting the emptying of each vessel.

FIG. 8. Schematic view of a method of manufacturing a fertilizer in themanner of the embodiments as in FIG. 4 but with the substitution ofthree pressure vessels in order to operate the processes in a“continuous batch” manner. The use of three vessels is such that onevessel is being filled, one is reacting and the third is emptying.

FIG. 9. Schematic view of the Pellet Beneficiation (“PB”) processembodiment of the present invention showing the use of heat-driedbiosolids pellets or granules in the manufacture of granular highnitrogen organically-augmented inorganic fertilizer.

FIG. 10. A flow diagram representation of Example 1 illustrating apreferred embodiment, showing the amounts of solids and water throughoutthe various steps of the AM process in an embodiment of the presentinvention as practiced for a 3 ton per hour of sludge input (in thisexample the percent solids of the input sludge or biosolids was 22 wt. %solids). This example also shows the details of the airflow and airtreatment scheme practiced in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are directed to methods ofmanufacturing a fertilizer, especially a high nitrogen containingorganically-augmented inorganic ammonium based fertilizer. Otherembodiments are directed to the fertilizers manufactured by thesemethods. Embodiments of the present invention take advantage of thethixotropic property of many types of dewatered biosolids or organicsludges to become pastes or paste-like pumpable fluids when vigorouslymixed, back-mixed and folded or sheared.

As shown in FIG. 1, the fertilizer manufacturing plant (105) is sized toservice the needs of the community (101) in which it is sited. Thistailoring design results in a small biosolids processing/fertilizermanufacturing plant being constructed, e.g., processing less than 10tons per hour of dewatered sludge and preferably processing between 3and 6 tons per hour of dewatered sludge, which also reduces costs, makesit easier to standardize with standard sized interchangeable equipmentand, because the manufacturing plant is small, improves the logistics ofoperation and liability. Because the fertilizer manufacturing plants ofseveral embodiments of the present invention usually have associated andadjacent storage facilities which can serve as local or regionalfertilizer warehouse facilities (105), access to the fertilizer productof the present invention is facilitated. Having a local warehouse sitealso further improves logistics associated with the fertilizer industryin that several embodiments of the invention produce a high-nitrogenfertilizer that can be shipped shorter distances to fertilizerdistributors (106), end users or the growers (107), thereby reducingtransportation costs for the product as well as for the input biosolidsor organic sludge. An odor control system (104) can be incorporated intothe manufacturing plant design to ensure community acceptance of thefertilizer manufacturing plant and to facilitate meeting USEPA standardsas well as making the process more efficient through the capture andincorporation of valuable nitrogen or other potential fugitive plantnutrients from the process air of the plant.

Embodiments of the present invention are unique compared to traditionalfertilizer manufacturing practices in which a large manufacturingfacility is located as far away from communities as possible therebyrequiring that input materials be shipped over long distances to operatethe plant. A good example of this was the biosolidsconversion-to-fertilizer plant located in Helena, Ark. which practicedthe manufacturing processes taught in U.S. Pat. Nos. 5,984,992;6,159,263; 6,758,879; and 7,128,880. For this fertilizer manufacturingplant, the biosolids were shipped all the way from New York City andWestchester County, N.Y. at a significant cost to the manufacturingprocess. Embodiments of the present invention eliminate this type ofproblem by arranging the physical equipment necessary to perform theclaimed process adjacent or close to the source of dewatered biosolidsor other organic sludges. Such sources of dewatered biosolids or otherorganic sludges are typically municipal wastewater treatment plants.

In addition, embodiments of the present invention have the advantagethat they may be interfaced with hot byproduct ammonium salt fertilizerproduction that is associated with unrelated commercial businesses suchas that of nylon or steel production. In these two industries, as isalso shown in FIG. 1, hot ammonium sulfate is a by-product (108) whichcan be directly added to a pressure vessel in an embodiment of thepresent invention.

Embodiments of the present invention can treat any organic sludge,preferably comprised of microorganisms, such as sludges selected fromthe group comprised of municipal dewatered biosolids (102), domesticseptage, pharmaceutical fermentation wastes and microbial digests ofother organic products such as food stuffs and/or animal manures ordigested animal manures. These sludges may be between 12% and 40% solidsand preferably between 18% and 30% solids. This treatment process canpreferably result in the production of a granular or pelleted USEPAClass A fertilizer product of suitable dryness, hardness and chemicalquality to produce a valuable, high-nitrogen, commercial fertilizerproduct that is capable of competing in the national and internationalmarketplace against traditional inorganic fertilizers. A commercial,high-nitrogen fertilizer preferably has greater than eight (8) percentnitrogen by dry weight of the finished fertilizer and more preferably atleast fifteen (15) percent nitrogen by dry weight of the finishedfertilizer. The Class A characteristic refers to the microbiologicalquality of the finished fertilizer product, which meets the UnitedStates Environmental Protection Agency Class A microbiological standardsfor a product containing municipal biosolids as defined in 40 CFR Part503. Embodiments of the present invention meet or exceed this standardon the basis of the stress condition and the retention time utilized,and on the basis that the finished fertilizer is greater than 80%, andmore preferably greater than 90% dry solids with the optimal level beingover 98% dry solids in composition, ensuring that the associated USEPAVector Attraction Standards are met (i.e., 90% or greater) and that thefinished fertilizer granule is optimized for minimal water contentincreasing hardness characteristic and eliminating water with respect totransportation of the finished fertilizer. Hardness is provided byadding to the fertilizer mix prior to shaping one or more hardeningagents selected from the group consisting of ferric oxides, alum,attapulgite clay, industrial molasses, lignon, ligno sulfonate, ureaformaldehyde polymerization and combinations thereof

Embodiments of the present invention produce a safe, sterile mix orfertilizer preferably exceeding the minimum requirements of a USEPAClass A biosolids-containing product. Embodiments of the presentinvention utilize a stress condition and a retention period that createan autoclave effect over extended temperature and pressure exposures.This autoclave effect can destroy by sterilization any microorganismspresent in the sludge, including bacteria, viruses, fungi, parasites,and parasite eggs. In addition, embodiments of the present invention arepreferably designed to hydrolyze many macromolecules that may also be inthe sludge. Stress conditions which can include, but are not limited tothe pH of the mix, elevated pressure, and elevated temperature, combinedwith a controlled retention period result in a mix and/or a fertilizerthat is safer compared to products processed utilizing pipe-crossreactor technologies. For example, embodiments of the present inventioncan utilize a retention period within the pressure vessel of greaterthan 1 minute and preferably greater than 5 minutes and more preferablygreater than 20 minutes. Ability to control the retention period isvaluable because when the sludge is subjected to the stress conditionfor a longer time, a better treatment of the sludge results. Byadjusting the retention period and the stress conditions it is possibleto vary the level of treatment and thereby control the properties andquality of the resulting mix or fertilizer.

A series of mixers is often employed in embodiments of the presentinvention. These mixers may optionally be heated, e.g., single shaftedor double shafted pugmill type mixers, preferably a blending and mixingpugmill utilizing an adjustable broad-shaped blade configuration.

Embodiments of the present invention produce fertilizer with amounts ofarsenic, cadmium, copper, lead, mercury, molybdenum, nickel, seleniumand/or zinc well below levels of harm and less than the ExceptionalQuality (“EQ”) standard for metals as published by the USEPA forproducts containing municipal biosolids.

Because of exceeding this regulation and the hydrolyzing conditions ofthe hydrolyser or pressure vessel for macromolecules (e.g., personalpharmaceutical products such as antibiotics or hormones or hormone-likesubstances), the resulting fertilizer is safer for use in and aroundfarming, plants, and animals. Further, it is safe for handling by andaround humans.

FIG. 2 provides a schematic diagram of an embodiment of the presentinvention, wherein the process of this embodiment utilizes dewateredmunicipal biosolids combined with ammonium salt fertilizers. In thisembodiment, the sludge to be treated is a dewatered biosolid, oftenreferred to as a “biosolids cake.” This biosolid is delivered to themanufacturing facility and conditioned. The conditioning takes place inan initial mixer or pugmill by a vigorous mixing which converts thethixotropic sludge or biosolids into a pumpable mix or paste orpaste-like mix. While in the mixer or pugmill, an oxidizing agent, andan amount of concentrated acid, preferably phosphoric acid, is added.The oxidizing agent reacts with reduced sulfur compounds and otherodorants present in the biosolids. The concentrated acid slightlyacidifies the biosolids and, if phosphoric acid, assists in modifyingodorants present in the sludge. Optionally, the biosolids can be heatedduring this conditioning process by exposure to heat in heat-jacketedmixers and or in mixers with hollow mixing blades which may containheated oil to effect heat transfer. After conditioning, the biosolidsare transferred to a pressure vessel wherein concentrated acid and anitrogen source are simultaneously added. In this embodiment of theinvention, the nitrogen source comprises a base, such as anhydrous oraqueous ammonia. A mix of biosolids and ammonium sulfate and ammoniumphosphate is formed. This mix is maintained in a stress condition for aretention period. The stress condition includes elevated temperature,and elevated pressure. The elevated temperature is often due to anexothermic reaction of the components, which can increase thetemperature of the mix to 212° F. or greater. At such temperatures,steam is generated from the mix. This steam is allowed to exit thepressure vessel under valve-controlled release, accomplishing a partialdrying of the mix. The stress condition and the retention period arecontrolled so as to result in the production of a mix that is sterileand that contains hydrolyzed macromolecules from the biosolids. Controlof the stress condition and the retention period also results in thefusion of the ammonium ions formed with the organic molecules presentcreating a natural slow-release property for the nitrogen present, andthe denaturization and or hydrolysis of many macromolecules present inthe biosolids, such as proteins. When such molecules are biologicallyactive, this denaturization and/or hydrolysis renders them less activeor inactive thereby creating a safer mix for public usage or exposure.

Alternatively, instead of simultaneously adding the concentrated acidand the nitrogen source to the pressure vessel, a hot melt or salt ofammonium sulfate and or ammonium phosphate can be substituted toaccomplish the same effects as the above addition of simultaneous acidand ammonia. As an option, when this alternative is utilized is forphysical heat to be applied to the pressure vessel.

In one embodiment, the mix is subsequently transferred from the pressurevessel to a second mixer or pugmill, where it is mixed with a hardeningagent or agents, as well as with additional nutrients if required. If amelt was formed in the pressure vessel from partial ammoniation withexcess acid, the mix is also sparged with an additional amount of anitrogen source comprising a base, such as ammonia, preferably vaporizedammonia in order to complete the ammoniation thereby forming ammoniumsalt.

In embodiments of the present invention, it is preferable to convertliquid ammonia to vaporized ammonia prior to entering the spargers inboth the pugmill that follows the pressure vessel and the granulator.This conversion to vaporized ammonia improves operation of the plant aswell as reducing energy requirements. The liquid anhydrous ammonia isconverted to superheated ammonia vapor by means of a heater in order tocomplete the ammoniation process started in the pressure vessel. Thisheating means may be a direct heater applied to the ammonia deliveryline or may be a heat exchanger installed to recover excess heat fromelsewhere in the process of this invention. This may be, for example, inthe dryer discharge air stream downstream of the baghouses and prior tothe acid scrubbers. The ammonia side of the vaporizer is controlled at90 to 120 psig, and preferably at 100 psig (ammonia saturated at 64°F.). The ammonia vapor is superheated with the temperature controlled at120-200° F. and preferably at 170-180° F.

Replacing liquid ammonia with vaporized ammonia in the recyclepugmill/granulator ammonia spargers provides several benefits: itcompletes the ammoniation process started in the pressure vessel; itimproves reaction efficiency by increasing surface area of ammonia tocontact unreacted acid; it increases energy efficiency by using wasteheat from the process to increase the temperature of the granulatorstream thereby increasing evaporation in the granulator and reducingdryer energy required; it reduces dust creation and increases granulesize and hardness by providing even distribution of ammonia to thereaction zone in the pugmill/granulator (droplets of liquid ammonia cancreate dust when small localized areas of high pH are created in theuncured granules, and vapor ammonia eliminates this problem); it reducesthe required water quench by cooling the dryer discharge gas stream andutilizing the heat; or combinations thereof.

Next, the mix is further treated by granulation or extrusion intogranules or pellets. The granules or pellets are dried and passedthrough one or more screens to separate oversized materials andundersized materials from proper-sized materials. The oversizedmaterials can be crushed in a crusher or mill. Subsequently, theundersized materials and the crushed oversized materials can be recycledto the second mixer or pugmill to facilitate the pelletization orgranulation of the fertilizer mix into pellets or granules. Theresulting proper-sized pellets or granules are then dried, sized,coated, cooled and stored.

It is noted that, when a traditional granulator is used in the shapingprocess, ammoniation by vaporized ammonia and recycle addition may occurin that vessel as well.

Water removed from the mix as steam from the pressure vessel and fromsubsequent vessels as steam and/or water vapor may be condensed andpreferably returned to the waste water treatment plant (WWTP), or may betreated and discharged into adjacent water resources, or into theatmosphere.

A further embodiment of the invention is directed to treating a sludgeby first conditioning the sludge by mixing it with a force sufficient tomake it pumpable. The sludge can be further conditioned by adding one ormore oxidizing agents and/or by adding one or more acids to reduce thepH of the sludge. The conditioning typically occurs in a mixer or apugmill, which can optionally be heated. The conditioned sludge is thenadded to a pressure vessel. Subsequently or simultaneously once theprocess reaches steady-state, one or more acids and one or more nitrogensources are combined within a reaction zone located within theconditioned sludge. The reaction zone is an area of optimal applicationof any acid, any base, any nitrogen source, and any combination thereof,in order for the sludge to be treated in embodiments of this invention.The reaction zone is optimized based on the size of the vessel intowhich the sludge is placed. The reaction zone size varies depending onthe inflow of acid, base, and/or nitrogen source, as well as on theviscosity of the sludge. The reaction zone is essentially located in thebottom portion of the sludge in the pressure vessel, preferably as lowas possible, so that the weight of the materials in the vessel pressesdown on it, thereby helping to contain any force generated by theexothermic reaction. The reaction zone is the portion of the sludge intowhich acids, bases, and/or nitrogen sources are injected. Use of theterm “reaction zone” is not intended to imply that reaction occurs onlywithin the reaction zone. While the initial combination of the reactivecomponents and the initial exothermic reaction occurs in the reactionzone, it is expected that exothermic reaction continues to occurthroughout the vessel. At least one of the one or more nitrogen sourcescomprises a base, and so an exothermic reaction can take place betweenthe acid and the base. Subsequently, this mix is maintained in a stresscondition for a retention period. The stress condition can result in thepartial hydrolysis and/or denaturation of any macromolecules includingproteins contained in the sludge component of the mix. The stresscondition can also result in the partial hydrolysis and/or denaturationof any personal pharmaceutical compounds, antibiotics, hormones,hormone-like molecules, or other biologically active compounds. Thestress condition and the retention period can create an autoclave effectover extended temperature and pressure exposures that destroys bysterilization any microorganisms present in the sludge, includingbacteria, viruses, fungi, parasites, and parasite eggs. The stresscondition can include agitating the mix, an increase in temperatureand/or pressure due to any exothermic reaction of the components of themix. Any temperature increase of the mix due to the stress conditionpreferably exceeds 85° C. (185° F.), more preferably exceeds 100° C.(212° F.), more preferably exceeds 121° C. (250° F.), and mostpreferably exceeds 126° C. (260° F.). Any pressure increase of the mixdue to the stress condition preferably exceeds 20 pounds per square inch(psi), more preferably exceeds 30 psi, and most preferably exceeds 38psi.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising conditioning via agitation andoxidation and initial acidification of an amount of bioorganic sludgesuch as a municipal dewatered biosolids; mixing concentrated acid withammonia simultaneously in the presence of the conditioned biosolids tocreate an ammonium melt (a partially ammoniated mix) in a pressurevessel under controlled temperature, atmospheric pressure, mix retentiontime and water removal as steam and/or water vapor; and furtherprocessing said hydrolyzed mix via an additional mixer, blending inoptional additional conditioners, such as an iron oxide, and at leastone hardener into the fertilizer mixture to control hardness; andsparging said additional mixer with additional vaporized or gaseousammonia to complete the salt formation of ammonium sulfate and/orammonium phosphate and following that via traditional granulationprocessing to create a granular organically-augmented inorganicfertilizer in the plant. Said sparging of vaporized ammonia may also becarried out in the granulator as is practiced in the manufacturing ofgranular fertilizers. When calcium ferrate or potassium ferrate orsodium ferrate or when iron oxide is added to the mix, the iron is alsoserving as an important nutrient in the finished fertilizer which bothenhances the value of the product and its performance fertilizing targetcrops.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising conditioning via agitation andoxidation an amount of bioorganic sludge such as a municipal dewateredbiosolids; mixing concentrated acid with ammonia simultaneously in thepresence of the conditioned biosolids to create an ammonium salt in apressure vessel under controlled temperature, atmospheric pressure, mixretention time and water removal as steam and/or water vapor; andfurther processing said hydrolyzed mix via an additional mixer, in anadditional mixer blending in optional additional conditioners, such asan iron oxide, and at least one hardener into the fertilizer mixture tocontrol hardness ammonium fertilizer art and following that bytraditional granulation processing to create a granularorganically-augmented inorganic fertilizer in the plant.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising mixing a thixotropic organicsludge to produce a pumpable paste-like mix; treating the mix with oneor more oxidants and acidifying the thixotropic paste in a mixer toproduce a first conditioned mixture; obtaining a high temperatureinorganic fertilizer melt comprised of partially ammoniated mixcontaining ammonium sulfate and or ammonium phosphate with excess acid;blending the hot melt with the conditioned mixture to produce a secondmixture in a pressure vessel with a temperature over 85° C. (185° F.)and preferably over 100° C. (212° F.) under controlled atmosphericpressure and mix retention time and removing water (as steam and watervapor) from said mix; further processing said second mix in anadditional mixer to blend in optional additional conditioners, such asan iron oxide, and at least one hardener into the fertilizer mixture tocontrol hardness and sparging said additional mixer with vaporizedammonia to complete the salt formation of ammonium sulfate and orammonium phosphate; continuing to remove water from the third mixture toproduce a material that can be further processed with traditionalgranulation processing or extrusion technologies; and creating an endproduct fertilizer from the third mixture. Said sparging of vaporizedammonia may also be carried out in the granulator.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising mixing a thixotropic organicsludge to produce a pumpable paste-like mix; treating the mix with anoxidant and acidifying the paste in a mixer with phosphoric acid toproduce a first mixture; obtaining a high temperature inorganicfertilizer salt comprised of ammonium sulfate and or ammonium phosphate;blending the hot salt with the first mixture to produce a second mixturein a pressure vessel with a temperature over 85° C. (185° F.) andpreferably over 100° C. (212° F.) under controlled atmospheric pressureand mix retention time and removing water (as steam and water vapor)from said mix; blending in optional additional conditioners, such as aniron oxide, and at least one hardener into the fertilizer mixture tocontrol hardness; continuing to remove water from the third mixture toproduce a material that can be further processed with traditionalgranulation processing or extrusion technologies; and creating an endproduct fertilizer from the third mixture.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer comprising mixing a thixotropic organicsludge to produce a pumpable paste-like mix; conditioning the mix withone or more oxidants, preferably calcium ferrate, in a first pugmill ormixer (pugmill A in FIG. 5) to produce a first alkaline mixture; thendischarging this conditioned mix into a second pugmill or mixer (pugmillB in FIG. 5) into which an ammonia source is added. In this embodiment,aqueous ammonia is used as the base. This second mixer then dischargesits alkaline ammoniated mix into the pressure vessel. The pressurevessel will receive a concentrated sulfuric acid to produce a hightemperature inorganic fertilizer melt comprised of ammonium sulfate. Inthis embodiment phosphoric acid is also added to the pressure vessel,which produces ammonium phosphate. The phosphoric acid is added to thepressure vessel rather than to the first pugmill as with otherembodiments because to add it early in the first pugmill would thenproduce an undesirable exothermic reaction in pugmill B The exothermicreaction in the pressure vessel achieves a temperature over 100° C.(212° F.) and preferably over 280° F., under controlled atmosphericpressure and mix retention time and removing water (as steam and watervapor) from said mix; discharging the fertilizer mix to an additionalpugmill or mixer therein using vaporized ammonia to complete theformation of ammonium salts and blending in optional additionalconditioners, such as an iron oxide, and at least one hardener into thefertilizer mixture to control hardness; continuing to remove water fromthe third mixture to produce a material that can be further processedwith traditional granulation processing or extrusion technologies; andcreating an end product fertilizer from the third mixture.

Alternatively, this embodiment of the invention is directed to methodsof manufacturing a fertilizer comprising mixing a thixotropic organicsludge to produce a pumpable paste-like mix; conditioning the mix withone or more oxidants, preferably calcium ferrate and acidifying thepaste in a first pugmill or mixer (pugmill A) with phosphoric acid toproduce a first mixture; then discharging this conditioned mix into asecond pugmill or mixer (pugmill B) into which flows concentrated acidor aqueous ammonia, but not both. This second mixer then discharges itsmix into the pressure vessel. The pressure vessel receives an ammoniasource thereby obtaining a high temperature inorganic fertilizer meltcomprised of primarily ammonium sulfate with a smaller amount ofammonium phosphate with a temperature over 100° C. (212° F.) andpreferably over 280° F., under controlled atmospheric pressure and mixretention time; removing water (as steam and water vapor) from said mix;discharging the fertilizer mix to an additional pugmill or mixer thereincompleting the formation of ammonium salts using vaporized ammonia andblending in optional additional conditioners, such as an iron oxide, andat least one hardener into the fertilizer mixture to control hardness;continuing to remove water from the third mixture to produce a materialthat can be further processed with traditional granulation processing orextrusion technologies; and creating an end product fertilizer from thethird mixture.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer in the manner of the above embodiments butwith the substitution of heat-dried biosolids or organic sludges for thedewatered biosolids cake described above and as illustrated in FIG. 9.This dried biosolids material may range in solids from 30% to 99.9% butpreferably and more commonly range from 90% to 99% in order to beclassified as Class A by the USEPA as governed by their VectorAttraction rules for biosolids or biosolids-containing material. Thedried biosolids or organic sludge material, if received as pellets orgranules, must be milled to a powder before the addition of some waterand subsequently exposed to an oxidation agent and acidification duringconditioning. The conditioned sludge can then be processed through theremainder of the process as described in the above embodiments.

Another embodiment of the invention is directed to methods ofmanufacturing a fertilizer in the manner of the above embodiments butwith the substitution of three pressure vessels in order to operate theprocesses in a “continuous batch” manner as in FIG. 8. The use of threevessels is such that one vessel is being filled, one is reacting and thethird is emptying. Such employment of multiple vessels allows control oftemperature and atmospheric pressure and retention time during thereaction phase of the process. The addition of chemicals, mixing,reactions, ammoniation, removal of water and granulation or extrusionwould occur as described for any of the above embodiments.

An additional embodiment of the present invention accepts dewatered ordried biosolids but does not condition them in the manner described inthe above embodiments. Instead, the biosolids are simply agitated to apumpable state; optionally water may even be added if necessary. Thesepumpable biosolids are then processed as in the above embodiments. Theoxidation agents and optionally, additional phosphoric acid for pHcontrol, nutrient addition and suppression of auto-oxidation may beadded in the second mixer or pugmill that follows the pressure vessel ormay be eliminated completely. The remainder of the processing of thisbiosolid will be as described for the embodiments described above. Sucha method is not considered as optimal as the other embodiments but is apotential method for producing a high nitrogen containing bioorganicaugmented inorganic fertilizer.

The diagram in FIG. 3 contributes additional details to the AMmanufacturing process initially described in FIG. 2 and describes indetail the preferred embodiment of the present invention as in FIG. 4.The process in FIG. 3 shows that the incoming biosolids or organicsludge may be of varying percent solids ranging from 17% to 32% solidsin the AM process for dewatered biosolids. [In another embodiment ofthis process described in detail later, and in FIG. 9, and referred toabove as the PB process, biosolids that have been further dried can alsobe processed to high nitrogen containing fertilizers. In this PBembodiment, the biosolids can range from 33% solids to 100% solids. Whenthey are of a dry solids nature, they are milled to a powder and thenprocessed further.]

FIG. 3 shows the biosolids being delivered to the AM plant in the rangeof 12% to 40% solids with biosolids between 18% and 30% more common.This delivery may be either through conveyors or pipes from thewastewater treatment plant (“WWTP”) or by traditional transportationusing truck, train or barge. Upon arrival at the plant, the dewateredsludge (301) is passed through a lump breaker or screening device toremove large foreign objects that might damage or destroy pumps or otherequipment in the process. The sludge placed into a surge or holding tankor silo or a live bottom bin for accumulation and storage untilprocessed. Preferably, the delivered solids may be placed in a holdingtank or silo and then transferred to the first mixing apparatus forconditioning.

If the biosolids have not been screened for contaminant removal prior tosurge storage, then they are next preferably passed through a lumpbreaking apparatus or screen device (302) to remove any metal or rock orother large foreign objects to protect the pumping and blendingapparatuses later used in the process. The solids are then transferredby screw conveyor or pump to the first mixing or conditioning apparatus(303). This solids conditioning apparatus is preferably a dual-shafted,jacketed (for optional heating) pugmill containing blades angled in sucha way as to mix the contents of the pugmill thoroughly as the contentspass through the horizontal length of the pugmill. The mixing process(308) initially conditions the thixotropic dewatered biosolids bytreating it with sufficient mixing and agitation energy that a pumpablepaste is created. This material is then conditioned further with anoxidizing agent (306) which may be selected from the group, calciumferrate, sodium ferrate, potassium ferrate, ozone, hydrogen peroxide,calcium hypochlorite, sodium hypochlorite, potassium hypochlorite,chlorine dioxide and oxygen itself as well as with mixtures of saidoxidants. In the preferred embodiment of the present invention describedin FIG. 3 calcium ferrate is injected into the initial mixing apparatusor pugmill for the purpose of oxidizing reduced sulfur compounds presentin the biosolids as well as other odorants therein contained. Thisferrate oxidative agent is very effective at destroying the odorantspresent in the biosolids when used at 1 to 10 percent and preferably at2 to 5 percent of the volume of wet biosolids entering the pugmill #1.Further, the calcium ferrate (and/or other ferrates) can begin thehydrolyzing process for the partial degradation or denaturization ofmacromolecules contained in the biosolids such as proteins. Further, theconditioning process conducted within the initial pugmill also includesthe introduction of a concentrated acid (304), preferably phosphoricacid (310) and more preferably with concentrated phosphoric acid of atleast 50% strength creating an acidic paste within the initial mixer.Optionally, process water and blowdown water from the air scrubbingapparatus can be infused into the initial mixer, or they may be infusedinto the sludge immediately prior to the lumpbreaker if necessary. It isthe intent of the present invention to minimize the amount of wateradded into the manufacturing sequence in order to reduce the energyrequirements needed for dewatering.

Mixing with oxidizing agent(s) and concentrated acid, preferablyphosphoric acid, begins the process of odor control and acidifies thebioorganic material to a level of between pH 4.0 and pH 6.9, preferablybetween pH 4.5 and pH 6.0. This treatment with phosphoric acid alsoprovides a level of resistance to oxidative heating that occurs uponlong term storage of finished organic-containing granules, such ascommonly occurs with heat-dried biosolids pellets. Heating and mixing(311) in this initial conditioning apparatus will create a pumpablepaste (308). In one embodiment of the present invention, this paste ispreferably heated to control odors and prepare the biosolids for mixingwith concentrated acid and ammonia in a pressure vessel. Saidconditioning heat is preferably imparted to the biosolids by means of aheated mixing apparatus wherein the heat is transferred by a heatedshaft, heated paddle blades or by a heated jacket surrounding the mixingapparatus body. The mix may be heated to 80 F, preferably to 95 F andmore preferably to 111 F. Additionally, some heat is imparted duringconditioning from the addition of the oxidation agent and theconcentrated acid.

Although the paste or mix exiting this initial mixer may be of ambienttemperature, it is preferred that the paste or mix exiting this initialmixer achieve the temperature of 27° C. (80° F.), preferably 35° C. (95°F.) and more preferably exceed 44° C. (111° F.). At a temperature of 44°C. (111° F.) the destruction of microorganisms is commenced. Allelevated temperatures will confer enhancement of fluidity and plasticityof the mix, facilitating the conditioning process itself as well as thesubsequent interaction with acid and ammonia in the pressure vessel. Theestablishment of higher than ambient temperatures in the bioorganicmaterial ensures that the heat energy contained in the ammonium salts isadvantageously used to kill or sufficiently inactivate at least allharmful pathogens (e.g. bacterial, viral, fungal and parasiticpathogens) that were contained in the bioorganic material, especiallymunicipal biosolids, especially when aqueous ammonia is used to form theammonium sulfate or ammonium phosphate as less exothermic energy isreleased when the aqueous ammonia is applied.

Pugmills or mixers (303, 314) are horizontal mixing chambers havingblade-shaped blending elements mounted on a powerfully driven shaft orshafts that rotate at a high speed which divide, mix, back-mix andre-divide the materials to be blended multiple times a second to yield athorough, uniform blend with reliable consistency. The blenders,pugmills and or mixers used in the processing sequence may be eachindependently heated via a heated shaft and or heated hollow screw blademechanism or heated by means of a jacketed sleeve around the apparatus.Heating is adjustable to provide a heated paste prior to blending withthe hot ammonium salt. Heating can also be optionally applied to thesecond mixing apparatus (314), preferably a pugmill especially whenaqueous ammonia is used, wherein hardeners, optional pH adjustmentagents as in vaporized or gaseous ammonia sparging, and dry recycle areadded.

Conditioning guarantees a mix with the proper consistency for injectioninto the pressure vessel. In the preferred embodiment of the presentinvention, anhydrous (99% ammonia) and if necessary as might be requiredby permit considerations, aqueous ammonia (305) is blended withconcentrated sulfuric acid (309) with or without concentrated phosphoricacid, in a pressure vessel (313). This reactor has been modified for thepurposes of this invention from the preneutralizer vessel commonly usedby the fertilizer industry, especially prior to the development of thepipe-cross reactors and as described by the IFDC in the FertilizerManual and by Sephri-nix in the Fertilizer Technical Data Book. Themodification is an alteration of the preneutralizer vessel described bySephri-nix on page 194 of the Fertilizer Technical Data Book.Specifically, the vessel in the Example 1 of the present invention isdesigned to have a single diameter and to receive the conditionedbiosolids at the base of the vessel and both sulfuric acid and ammoniadirectly above the biosolids input. The acid and the ammonia will reactforming ammonium sulfate and ammonium phosphate thereby forming afertilizer mix with the interaction of conditioned mix, the ammoniumsulfate and or the ammonium phosphate. In the preferred embodiment ofthe present invention a melt will be formed by partially ammoniating theacid in this vessel. This will improve the fluidity of the fertilizermix as compared to forming a salt with complete ammoniation of theinjected acid and facilitate the discharge of the fertilizer mix to thesecond pugmill in the manufacturing sequence (314).

The melt of ammonium sulfate/phosphate is preferably at a temperaturegreater than 100° C. (212° F.) and preferably at a temperature greaterthan 121° C. (250° F.) and more preferably at a temperature of greaterthan 126° C. (260° F.). In the pressure vessel the contact timenecessary shall be for a minimum of one (1) minute with the preferredrange of 5 to 30 minutes or more with a more preferred range of 10 to 20minutes with a preferred retention time for normal operation being about15 minutes.

It is anticipated that the pressure vessel will contain an agitationcapability as shown in FIG. 6 using rotating paddles or blades. Suchagitation of the mix within the pressure vessel will help ensureuniformity and controlled reaction of the mix. The agitation will alsoprevent consolidation of the mix and will facilitate discharge of themix into the second pugmill.

The orientation of the pressure vessel (313) is vertical with steambeing released by controlled valve at the upper end of the vesselthereby permitting the atmospheric pressure within the vessel to becontrolled. Further, this pressure, greater than 20 psia, and preferablygreater than 30 psia, and more preferably greater than 38 psia, combineswith the temperature and pH maintained within the vessel such thatchemical alterations of macromolecules occur within the vessel. Suchchemical alterations due to combined heat and pressure includes partialdenaturization of protein molecules and the hydrolysis of some proteinmolecules and the hydrolysis of other organic compounds. Suchdenaturization or hydrolysis of organics results in the creation of asafer final product because of the loss of biological activity oftenassociated with such compounds such as personal pharmaceuticals,antibiotics, hormones and other biologically-active organic compoundsthat were present in the biosolids.

In addition, it should be recognized that the high stresses created inthe pressure vessel (313), i.e., pressure and temperature of theinvention sterilizes the bioorganic materials for a safer, less harmfulfertilizer. Sterility is measured by lack of detection of viablemicroorganisms.

Following achievement of said times of exposure the venting of the steamand water vapor emitted from the mix and the pressure vessel can takeplace thereby partially drying the mix from the energy imparted into themix from the chemical reaction of acid and ammonia.

Drying of the mixture continues in the second mixer or pugmill thatfollows the pressure vessel (314) and may continue in the shapingapparatus such as the granulator, to be completed in a dryer (323), asin a rotary drum dryer or fluidized bed dryer. Ammoniation is completedin the second mixer or pugmill that follows the pressure vessel byinjection of vaporized ammonia or may be optionally completed byinjection of vaporized or gaseous ammonia into the granulator.

In one preferred embodiment, the process air is acid scrubbed to removeany fugitive odorants and especially vaporized or gaseous ammonia. Thecaptured ammonia, as an ammonium salt is mixed into the initial pugmillor mixer thereby increasing the efficiency of the entire system andmaximizing the final nitrogen concentration in the finished fertilizer.Miscellaneous residuals including dust (335), non-specification orreclaimed product (336) and dried fertilizer that is too small orundersized (327) or oversize material (329) that is crushed in acrushing or mill apparatus (330) or may include other additives, e.g.,iron (337) that a customer would prefer be added to the composition ofthe finished fertilizer are added to the second pugmill or mixer (314)positioned downstream from the pressure vessel.

Prior to the completion of the drying process, a hardener or hardeners(316) which help to agglomerate the mix and contribute to the hardnessof the dried pellet or granule (324) are added at the second pugmill(314). The hardener or hardeners are selected from the group comprisedof attapulgite clay, lignon, industrial molasses, and alum (225) amongothers or mixtures of these hardeners.

Optionally, dependent upon the requirements of the customer, additionalplant nutrients, (317) for example, potash or other forms of potassium,e.g., potassium hydroxide, are preferably added at the second pugmill.The solid nutrients that may be added also comprise urea, ammoniumnitrate, mono-ammonium phosphate, diammonium phosphate, and or potash.Also added in this second pugmill is any additional iron required. Thisiron may be of different valences, but the iron compound, known asmagnetite (Fe₃O₄), is preferable in this process. The iron contributesan important and valuable plant nutrient to the fertilizer mix

Also, additional ammonia may be sparged into this second pugmill (314)and into the granulator (319) to complete the formation of the ammoniumsalt and to control the pH of the mix and to facilitate the formation ofthe finished granule or pellet. The solids used to adjust the pH mayalso be principally alkaline agents selected from the group comprised ofcalcium carbonate, sodium hydroxide, calcium oxide, cement kiln dust,lime kiln dust, Class C fly ash, Class F fly ash, multistage burner ash,alum, alum sludge from water treatment and wood ash. These are added viascrew conveyors at specific rates for each compound. The liquidadditions also include pH adjustment materials such as acids, e.g.,phosphoric acid or sulfuric acid, or caustic solutions, e.g., sodiumhydroxide. These are pumped at respective rates to the injection ring toenter pugmill #2.

In addition, pH control agents (315) in addition to the vaporizedammonia added during sparging, may be added to this second mixer (314)in the form of one or more of group of alkaline materials such ascalcium oxide, calcium hydroxide, potassium hydroxide, or other metaloxides or metal hydroxides, anhydrous ammonia, cement kiln dust, limekiln dust, fluidized bed ash, Class C fly ash and Class F fly ashaddition to raise the pH of the mix. The fertilizer product of thepresent invention preferably has a pH of between 5.0 and 7.0, morepreferably between pH 5.5 and pH 6.5 (230), and more preferably betweenpH 5.7 and pH 6.3.

The remainder of the processing for shaping (319) as in pellet orgranule production (320) includes standard fertilizer granulationtechnology especially for high volume throughput plants. The pellet orgranule product, especially in smaller throughput plants considered tobe those of less than 25 tons product production per day, may involvemore innovative technologies such as injection or extrusion followed bymilling or spherulizing the pellet or granule or involves simpledischarge from a granulator or granulating pug mill. When a granulatoror granulating pug mill is used, it is preferable to feed some recycle(228), as in dry seed material, i.e., dry fines (327) and fines producedby the crusher or mill (330) or sub specification or reclaim material ofthe fertilizer product, into the second pugmill (314) and the granulatorto adjust the percent moisture present in the mix so that agglomerationor nucleation can occur resulting in granule formation.

Other preferred embodiments comprise adjustments to the processesdisclosed herein to control pH, dryness, nutrients in the product,shape, concentrations etc. to produce a plethora of fertilizers specificfor different plants such as roses, rhododendrons, and any otherflowers, vegetables, herbs, as well as products such as cat litters.Adjustments can also be made according to the geographic area in whichthe product is to be applied, to vary, for example, nutrients that maybe inherently or otherwise missing in the location. Examples of suchvariations include the addition of calcium, potassium or phosphorus indifferent amounts. Slow release fertilizers are the preferred embodimentof this invention.

In another preferred embodiment, the partially dry material is injecteddirectly into a vertical fluidized bed dryer to produce dry granules ina single step.

Normal drying (322) for final drying (323) is conducted using ahorizontal fluidized bed dryer, or a rotary drum dryer. The driedpellets or granules (324) which are greater than 90% solids andpreferably are greater than 95% solids and more preferably are greaterthan 98% and even more preferably are greater than 99½% solids are thensized (325) through one or more screens (326). The specification sizemay be varied dependent upon customer requirements, however, the rangeof suitable product for sale is between 0.7 mm and 3.2 mm with thecommercial range for normal sized fertilizer is between 2 mm and 3 mm.The present invention also can manufacture a minimal sized productsuitable for use in golf course applications which ranges from 0.7 mm to1.3 mm The proper sized material is separated and then coated and thencooled (331) in an apparatus (332), preferably a rotary drum, to lessthan 140 F, preferably to less than 130° F. and more preferably to lessthan 120° F. Coating the granule or pellet occurs optimally occurs inthe same vessel as cooling, usually a rotary drum apparatus usingambient air or cooled air as from an ammonia evaporation cooler. Coatingmay occur in a coating vessel specifically for that purpose prior toentering the cooling vessel. Coating is with a deduster or glazingmaterial which minimizes dust generation during transport, storage andapplication. The finished granule or pellet (333) is then conveyed tostorage (334) as finished high nitrogen containing bioorganic-augmentedinorganic ammonium fertilizer until shipment from the manufacturingsite. Properly coated and dried pellets or granules have a hardness ofgreater than 5 pounds crush resistance in order to resist dusting andhanding during transport, shipment and application. This coatingpractice also anticipates that when deduster coating or glazing materialis used it often requires a higher temperature, often 180 F, to maintaina molten condition for application in the coating apparatus.

The granule storage facility or warehouse, usually incorporating bins orsilos to contain the granules, must be dry to prevent agglomeration ofthe granules leading to degradation and destruction. The finishedproduct is a sterile fertilizer having substantially no detectableamount of viable microorganisms, such as E. coli or streptococci,harmful to animals or humans. Substantially no viable microorganismsmeans that the fertilizer is non-toxic and has no detectable amount or adetectable amount well below a threshold for safe handling and use ofmicroorganisms originating from the sludge or biosolids. Although thefertilizer is rendered sterile during manufacturing it can be expectedto be contaminated with air-borne microorganisms or by microorganismsdeposited by animal or other contamination during storage or use. In anycase, because the fertilizer product is dry and predominantly inorganicammonium salts it will not support microorganism multiplication at arate which would lead to a public health problem.

At times in the above embodiments it may be necessary during normaloperations to periodically shutdown plant equipment for inspection,repair, or replacement. This is done to different degrees depending onspecific situations. In one embodiment, shutdowns are automatic as in anautomated command sequence provided by the plant control processor; inanother embodiment, the shutdowns are carried out manually.

If a limited shutdown of the process is necessary to a single piece ofequipment such as the first pugmill, the flow of biosolids into thepugmill would stop and the unit would empty as much of the contained mixmaterial as possible into the feed pump and then to the pressure vessel.If the pugmill needs to be emptied further, a diverter valve closes andprocess water is used to flush the unit as well as the feed pump, withthe discharge flowing into the return fertilizer mix line, as shown inFIG. 7, and back to the biosolids surge tank. In this situation processwater is blocked from entering the pressure vessel which continues torun and empty through its normal discharge. After the fertilizer mixdrops to below the normal discharge point, a diverter valve on thedischarge closes sealing off the pressure vessel normal discharge. Thediverter valve at the bottom of the pressure vessel then shifts,allowing the compressed air entering the head space of the pressurevessel to force remaining material into the return fertilizer mix line.If further cleaning is needed, process water is then injected into thepressure vessel to flush it out followed by compressed air to purge thewater. Cleanout of the second pugmill that follows the pressure vessel,the granulator, the dryer and all subsequent equipment is performed byrunning them until the vessels are empty.

The fertilizer of the present invention is preferably chemicallyadjusted to fit the needs of high nitrogen fertilizer requirementscontaining significant amounts of phosphate, sulfur and iron to enhancethe targeted nitrogen (N) content of between 8 wt. % and 18 wt. %percent by weight, and preferably 15 wt. %, permitting significantcommercial valuation.

FIG. 4 further describes the process outlined in FIG. 3 and asanticipated to be practiced as the primary embodiment of the presentinvention showing the passage of material through the sequentialequipment used manufacturing process, the additives needed to treat andmanufacture the finished fertilizer and the odor control systememployed.

In a modification of the preferred embodiment, two other oxidativematerials may be added at pugmill #1. Liquid hydrogen peroxide at 25 to50% concentration is added by control of a pump to between 1% and 5% ofthe biosolids delivery rate into pugmill #1 (17). Also, calciumhypochlorite, a solid, may be delivered by screw conveyor to apulverizing mill and then to an additive port at a rate equal to between1% and 5% of the volume of biosolids entering the pugmill #1. Anadditional odor control agent, iron oxide, Fe₃O₄, also known asmagnetite (9), a solid, is preferably added using a screw conveyor (21)at a rate (26) to a mill (29) to pulverize and powder these additivesprior to addition to pugmill #2. Use of the mill is important inoptimizing these solids materials for contact with the odorant moleculespresent in the biosolids. The iron added here not only serves as anadditional odor control agent it also serves as an important plantnutrient enhancing the usefulness and value of the finished fertilizerproduct.

In another embodiment of the present invention, the process is basicallyas described for previous embodiments except that a complete ammoniumsalt with no excess acid remaining is formed in the pressure orhydrolysis vessel. This then removes the necessity for ammonia spargingin the second mixer or pugmill and or the granulator.

In another embodiment of the present invention is basically as describedfor the previous embodiments except that a partially very hot ammoniatedmelt containing ammonium sulfate with or without an amount of ammoniumphosphate and excess acid is created in a separate vessel such as apreneutralizer or a pipe-cross reactor after which that melt is directlytransferred into the pressure vessel to impart heat and pressure suchthat the conditioned mix is sterilized. Ammonia sparging using vaporizedammonia may be carried out in the second mixer or pugmill and or in thegranulator to complete the ammoniation, pH control and creation of theammonia salt fertilizer.

In another embodiment of the present invention, the process is asdescribed in previous embodiments except that instead of a melt, acomplete ammonium salt of ammonium sulfate with or without ammoniumphosphate with no excess acid is manufactured in the pressure vessel. Nosparging of ammonia will be necessary in the second mixer or pugmill andor the granulator.

Another embodiment of the present invention is practiced as any of theabove embodiments except that instead of a dewatered organic sludge orbiosolids, a drier sludge, pellets, dry organic pellets or biosolids arereceived to be processed. Water may or may not be added to startingmaterials, which may have between 12-40% solids, or preferably 18-30%solids. The preferred dryness of this embodiment is greater than 90 wt.% solids, usually received as a heat dried biosolids pellet manufacturedat a municipal wastewater treatment plant. This dried pellet or granuleusually contains less than 6 wt. % nitrogen and more commonly, less than4 wt. % nitrogen, and therefore is not desirable in the commercialfertilizer distribution system. This embodiment teaches the conversionof such dried low nitrogen pellets or granules into a high nitrogenorganically-augmented inorganic ammonium fertilizer. The received drypellets or granules are milled to a powder to facilitate production of apumpable paste-like material using a combination of an oxidation agent,an acid and if necessary, the addition of water—preferably process orcondensed water from later steps in the process.

In another embodiment of the present invention as illustrated in FIG. 8of the present invention, the biosolids mix exits pugmill #1 and entersone of three pressure vessels. The receiving pressure vessel isdesignated PV-1. The biosolids mix moves into PV1 at a rate controlledby valves. Each of the three pressure vessels may be heated with hot oilpassing through a jacket around each of the three pressure vessels.During the filling operation, the biosolids mix is agitated by rotatingblades within the pressure vessel. Simultaneously with the addition ofbiosolids a liquid hot or molten ammonium salt mixture enters the PV-1at a rate controlled by valves. The ammonium salt mixture ismanufactured in a reactor (R1) by combination of concentrated sulfuricacid and or phosphoric acid with either anhydrous (99.5% concentration)or aqueous ammonia via a pump at a rate ranging between 18% and 28% inammonia concentration. The sulfuric acid is added with phosphoric acidvia pumps, respectively, such that the amount of ammonium sulfate andammonium phosphate created when mixed with the biosolids mix willproduce a high nitrogen fertilizer, for example, a 15% nitrogenconcentration by weight % in the final fertilizer product. Further thiscombination of sulfuric acid and phosphoric acid is controlled such thata small amount of acid is in excess of the amount of ammonia also addedto the reactor. This will permit the finished ammonium salt mix to havean exit pH of approximately pH 4 to pH 6.5. The size of the reactor isset such that sufficient resident time occurs for the reaction betweenthe acids and the added ammonia to go to completion with minimaldischarge of unreacted ammonia. If a melt is to be formed, then theamount of added ammonia is insufficient to react with all of the addedacid, and vaporized ammonia must be added in a later vessel.

The reaction between the concentrated acid or acids and the ammonia isviolently exothermic. The reaction creates high heat which maintains theresultant ammonium salt in the soluble molten state with any waterpresent in the form of superheated steam. This violent exothermicreaction also will create significant pressure within the pressurevessel. This ammonium salt mix has a temperature characteristic that isgreater than 100° C. (212° F.) and preferably at a temperature greaterthan 121° C. (250° F.) and more preferably at a temperature of greaterthan 126° C. (260° F.) dependent upon the nature of the ammonia beingused in the reaction. If anhydrous ammonia is used, the temperature willbe significantly higher than when aqueous ammonia, especially at 21% N,is used.

The temperature and fluidity of the ammonium melt or salt is maintainedsuch that when it is blended with the biosolids mix in the receivingpressure vessel, the temperature of the blend will exceed 100° C. (212°F.) and preferably exceed 126° C. (260° F.). The higher temperaturesfacilitate the hydrolysis of proteins and peptides in the biosolids inan acid environment creating advantageous properties to the finalfertilizer product that result in increased crop production compared tofertilizers that do not contain such organic material, i.e., ammoniumsulfate or ammonium phosphate or urea fertilizers.

When the fill cycle of the receiving pressure vessel is complete thepressure vessel is designated PV-2 or the reaction vessel. The time inthe reaction vessel equals the time that the biosolids took filling andmixing in PV-1. The retention time is greater than 1 minute and lessthan 20 minutes. Preferably the system is set up such that the residenttime in each vessel is at least 5 minutes. During the resident time inPV-2 the agitation blades are continually mixing the contents of thepressure vessel which because of the exothermic reaction occurring isunder significant pressure. This pressure is of the range of 20 to 45psia dependent upon the level of exothermic reaction permitted. Whenanhydrous ammonia is used with concentrated acids the pressure rangesfrom 25 psia to 45 psia. When aqueous ammonia at 21% N is used theatmospheric pressure ranges from 16 psia to 25 psia because of theincreased water present in the reacting mix. In this embodiment externalheat may be applied to the pressure vessel such that temperatures andpressures reach or exceed 260 F and 30 psia. When the resident time inPV-2 is completed the biosolids-ammonium blend in the pressure vesseland its contents are designated pressure vessel 3 or PV-3 for theemptying cycle. The emptying cycle is equal in time to the filling cycleand the reaction cycle. During the emptying cycle, the biosolids move topugmill or mixer #2.

In summary for this last embodiment, the reaction phase of the processof the present invention utilizes three pressure vessels, each of whichis capable of performing all the same functions, but each operates insequence such that one is filling, one is reacting and one is emptying,all at the same rate. This manufacturing system is considered a batchsystem with regard to the reactions that occur in the pressure vesselshence the need for at least three to be operating at the same time.

The following examples illustrate the practice of preferred embodimentsof the present invention, but should not be viewed as limiting the scopeof the invention.

EXAMPLE 1

In this example municipal anaerobically digested biosolids that had beenpreviously dewatered to 22% were received directly by conveyor for anadjacent wastewater treatment plant as illustrated in FIG. 4 anddiagramed in FIG. 10. The received biosolids are initially passedthrough a lumpbuster device to screen out large contaminating rocks ormetal and then into a large surge tank (24,000 gallon capacity) in thereceiving area of the fertilizer manufacturing plant. The biosolids exitthe surge tank to a positive displacement pump which then pumps thesludge at a rate of 6600 pounds per hour to the first pugmill (doubleshafted) for conditioning and mixing.

This manufacturing plant is set up so that on average 3 tons per hour ofwet biosolids at 22% will be produced over a year with the manufacturingplant operating at a 90% efficiency. In order to ensure this output theplant is operated on an hourly basis of 3.3 wet tons of biosolids inputper hour creating 3.8 dry tons of finished fertilizer product (sludge toproduct ratio of 1.15) at a fertilizer nutrient rating of 15-2-0-16-1-20(N—P—K—S—Fe-Organic in wt. % of the finished fertilizer). Thisfertilizer competes well on the national and international commodityfertilizer marketplace and carries a significant value.

This first pugmill is configured with double shafts with adjustableblade angles set for aggressive mixing of the thixotropic biosolids intoa pumpable paste-like material with both a rotary and back and forthaction. Heat is applied to the pugmill in this example via hot oil whichis maintained at 350° F. The hot oil flowed through a steel jacketsurrounding the pugmill and helps to warm the biosolids to approximately80 F by the time the biosolids exited from the pugmill as some heatingalso occurs from the addition of the oxidizing agent and from theaddition of acid in this initial pugmill. Next, calcium ferrate (anaqueous solution containing 4% ferrate ion) was pumped from a reservoirfilled from a ferrate generator supplied by Ferrate TreatmentTechnologies at the rate of 5% by volume of the biosolids, i.e., atabout 150 pounds of dry calcium ferrate per 6600 pounds of wetbiosolids.

Following the addition of the oxidizing agent a concentrated phosphoricacid (black agricultural grade at 54% P) was added to the biosolids inpugmill #1. This acid treatment acidified the biosolids and began theodor treatment, imparting some resistance to oxidative heating in thefinished granule and adding phosphate nutrient for later value.

The output of pugmill #1 is a conditioned, warm, blended mix. Its odorhad been reduced at this point in the process due to the oxidationtreatment. The conditioned biosolids mix exited pugmill #1 at just over8100 pounds per hour and entered the stainless steel brick linedpressure vessel. Concentrated 93% sulfuric acid is pumped into the lowerthird of the pressure vessel simultaneously with anhydrous ammonia(99.5%). A detailed drawing of the pressure vessel used in this exampleis shown in FIG. 6. A violent exothermic reaction occurs in the pressurevessel with the exothermic generation of 287 degrees F. of heatthroughout the vessel. This heat causes the water in the mix to convertto steam and the pressure in the vessel rises to about 40 psia. Thereaction between the acid and the ammonia creates an ammonium meltbecause the amount of ammonia added was insufficient to completelyammoniate the acid added, i.e., about 10% of the ammonia was withheldfor sparging (as vaporized ammonia) into the second pugmill and thegranulator later. The creation of a melt in this vessel increases thefluidity of the mix and facilitates the homogeneous mixing within thevessel which is helped by the rotary agitation of two large paddlemechanisms. The fertilizer mix is maintained in the pressure vessel for15 minutes. The agitation and the fluidity along with the high psia inthe head space of the chamber cause the fertilizer mix to exit thevessel and pass to the second mixer or pugmill.

The high temperatures, pressures and physical agitation within thepressure vessel facilitates the partial hydrolysis of proteins andpeptides in the biosolids in an acid environment creating advantageousproperties to the final fertilizer product. These properties includeincreased crop production compared to fertilizers that do not containsuch organic material, i.e., traditional ammonium sulfate or ammoniumphosphate or urea fertilizers and also safety. Because these stressescan disrupt biologically active compounds contained in the biosolids,the resultant material is safer for usage. Further, the heat andpressure will sterilize the fertilizer mix causing it to exceed theUSEPA Class A pathogen regulations for a biosolids-containing material.The fertilizer mix exiting the pressure vessel weighed just over 12800pounds. Over 600 pounds of water were flashed off as steam and watervapor from the pressure vessel.

In pugmill #2 about 40 pounds of dry iron oxide in the form of Fe₃O₄ wasadded from its silo to the fertilizer mix to bring the iron (Fe) totalto 1% wt. % in the final product. Additionally, about 460 dry weightpounds of a solution of commercially-obtained lignon, hardening agent,was pumped from its reservoir directly into the injection ring in theanterior end of pugmill #2. Pugmill #2 also received an amount ofammonia (as vaporized ammonia) equal to about 7% by weight of the totalammonia required for complete ammoniation of the acid added to thepressure vessel.

The pugmill #2 was long enough and had sufficient retention time andagitation via the preferred double shafted blending paddles to mix theadditives with the fertilizer mix and insure the retention of sufficientheat to achieve effective granulation in the granulator. In thepreferred pugmill apparatus, the pugmill is insulated to help retainheat in the contained mix. The percent solids of the fertilizer mix wascontrolled by adding dry recycle to this second pugmill. In this exampleover 54000 pounds of recycle at 0.5% moisture was added to the over12800 pounds of fertilizer mix in this second mixer. Because someadditional water was removed from pugmill #2 via steam and water vapor,about 48000 pounds of fertilizer mix at 11% moisture was discharged tothe rotary granulator. The granulator was operated at a ratio of about4.5 dry recycle to 1 part fertilizer mix.

The granulator contains a continuous bed of dry product to facilitatethe agglomeration of the input fertilizer mix into granules with thepreferred shape being spherical. In addition, in this example about 3%of the ammonia was finally sparged into the bed of the granulator tocomplete the ammoniation of the added acid. A smaller amount of steamand water vapor was removed from the atmosphere in the interior of thegranulator, in this example just over 170 pounds of water. Thisevaporated water joined that from the hydrolyzer vessel and pugmill #2to be treated by acid scrubbing in a venture scrubber. The retentiontime of the fertilizer mix in the granulator was approximately 4minutes. In this example just under 48,000 pounds of granules exited thegranulator into the rotary dryer.

The granular fertilizer mix exited the granulator at a percent solidsrange of 89% and the temperature of the exiting mix was about 190° F.prior to entering the rotary drum dryer for final drying to 99.5 wt. %solids. The retention time in the dryer was about 20 minutes with justover 5600 pounds of water being removed from the mix. The rotary actionof the dryer continues to facilitate the formation of rounded orspherical granules started in the granulator.

Approximately 47940 pounds of dry granular fertilizer was passed to thescreen system where the product size granules, i.e., 2.0 to 3.0 mmdiameter were removed for cooling and coating with hot deduster oil. Theundersized dry material was directly conveyed back to the second pugmillas a component of the recycle to increase solids in pugmill #2 prior tothe fertilizer mix entering the granulator. The oversized material wasconveyed to a hammer mill where it was pulverized and then returned tothe second pugmill as part of the recycle via covered conveyor. In thisexample, 7400 pounds of dry proper sized fertilizer product wasdischarged to the cooler-coating apparatus; 16500 pounds was returned tothe second pugmill as part of the recycle; just over 7100 pounds perhour of oversized material was conveyed to the hammermill and convertedto fines; and, just over 16,600 pounds per hour of fines were returnedto the second pugmill as recycle. In the preferred embodiment of thepresent invention, the screen mechanism can be set to separate a smallergranule size, approximately 1 mm in diameter. These smaller granules canbe processed similar to the larger product. These are advantageousbecause they can demand a higher price on the fertilizer market.

Coating dry granules is advantageous to prevent dust generation anddegradation of granules. The process air from the dryer, the granulator,the pugmill #2, the cooler, the oil coating apparatus and the productoversized mill was filtered in the bag house while still hot (about 116°C. or 240° F.) enough to carry the removed water as vapor. The exit ofthe baghouse was passed to a condenser where the air is cooled withwater so that the water vapor is converted to liquid water. This waterwas discharged to the local sewer to return to the local wastewatertreatment plant.

The hot saturated air outputs from the fluidized bed dryer, the screensystem, the product oversize mill and the exhaust from cooling/coatingdrum were passed through a bag house to remove particulates as part ofthe emissions control system of the process. The process air was thenpassed through a packed bed acid scrubber for additional cleaning,including ammonia removal to improve nitrogen capture efficiency and toprevent atmospheric ammonia discharge. The scrubbed air was then sent toa vertical quenching tower to condense the water out of the saturatedprocess air for discharge to the sewer to be returned to the wastewatertreatment plant. Alternatively, this water can be treated and dischargedto natural receiving waters.

The air from the quenching tower was then passed to a biotricklingfilter for final removal of nearly all odorants. The air from thebiotrickling filter was the passed through a biofilter and thendischarged directly to the environment. In this example approximately14,000 CFM were discharged. The biotrickling filter and the biofiltersystem operate by having contained microorganisms effectively andefficiently capture and remove by their catabolism the odorants andorganics from the scrubbed process air. The odor quality of thedischarged air would be judged very satisfactory to be located in anindustrial area or other appropriate community setting.

The dry hard (5.5 pounds hardness, i.e., the average downward pressurerequired to crush a single granule) granular fertilizer was determinedto be rated at 15-2-0-16-1-20, with each of these numbers representingthe wt. % of N—P—K—S—Fe-organics. Immediately prior to shipping thestored fertilizer granules were rescreened for final sizing and recoatedwith deduster or a glazing compound before being loaded in directly intotrucks, rail cars, barges or loaded into 1 ton super sacks fordistribution.

EXAMPLE 2

In this second example, the same 3.3 tons per hour of wet biosolids wereprocessed in the AM process as described for the preferred embodiment ofthe present invention, however, all the anhydrous ammonia was added inthe pressure vessel to complete ammoniation and formation of ammoniasulfate salt in the fertilizer mix. Although this fertilizer mix is notas fluid as when a melt is formed, the high head pressure and mechanicalagitation was sufficient to cause the hot fertilizer mix to exit fromthe pressure vessel as required. No additional ammonia was sparged intothe pugmill #2 or in the granulator in this Example 2. The remainder ofthe example is as was described for Example 1 with a similar qualityfertilizer being produced.

Other embodiments and uses of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. All references cited herein,including all publications, U.S. and foreign patents and patentapplications, are specifically and entirely incorporated by reference.The term comprising as used throughout this application includes themore limiting terms and phrases “consisting essentially of and“consisting.” It is intended that the specification and examples beconsidered exemplary only with the true scope and spirit of theinvention indicated by the following claims.

1. A method for treating a sludge comprising the steps of: (a)conditioning the sludge, (b) adding the conditioned sludge to a pressurevessel, (c) adding a reactive mixture, (d) maintaining the mix in astress condition for a retention period, wherein step (a) comprisesmaking the sludge pumpable.
 2. The method of claim 1, wherein thereactive mixture comprises a hot salt of a substance selected from thegroup consisting essentially of ammonium sulfate, ammonium phosphate andcombinations thereof.
 3. The method of claim 1, wherein the reactivemixture comprises a hot melt of a substance selected from the groupconsisting essentially of ammonium sulfate, ammonium phosphate andcombinations thereof.
 4. The method of claim 1, wherein the reactivemixture comprises the separate additions of concentrated acid and abase.
 5. The method of claim 1, wherein the reactive mixture comprisesthe separate additions of a sludge previously treated with aconcentrated acid and a base.
 6. The method of claim 1, wherein thereactive mixture comprises the separate additions of a previouslyammoniated conditioned sludge and a concentrated acid.
 7. The method ofclaim 4, wherein the concentrated acid is sulfuric acid, phosphoricacid, or a combination thereof.
 8. The method of claim 1, wherein thestress condition comprises agitating the mix and results in partial orcomplete hydrolysis, denaturation, sterilization, or combinationsthereof of components of the sludge.
 9. The method of claim 8, whereinthe components of the sludge are selected from the group consisting ofpersonal pharmaceutical compounds, antibiotics, hormones, hormone-likemolecules, other biologically active compounds, macromolecules includingproteins, and combinations thereof.
 10. The method of claim 1, whereinthe sludge is selected from the group consisting of municipal dewateredbiosolids, heat-dried biosolids, pharmaceutical fermentation wastes,microbial digests of organic products, food stuffs, food byproducts,animal manures, digested animal manures, organic sludges comprisedprimarily of microorganisms, and combinations thereof.
 11. The method ofclaim 1, wherein the sludge is a dry or dewatered sludge containingbetween 12% and 40% solids, between 18% and 30% solids, between 33% and99% solids, or between 90% and 99% solids.
 12. The method of claim 1,wherein the conditioning step comprises adding one or more oxidizingagents, one or more acids, or a combination thereof to the sludge. 13.The method of claim 12, wherein the one or more oxidizing agents areselected from a group consisting essentially of calcium ferrate, sodiumferrate, potassium ferrate, hydrogen peroxide, calcium hypochlorite,sodium hypochlorite, potassium hypochlorite, chlorine dioxide, ozone,oxygen, and combinations thereof, and wherein the one or more acidscomprise phosphoric acid, sulfuric acid, or a combination thereof. 14.The method of claim 1, further comprising the step of adjusting the pHof the mix.
 15. The method of claim 13, wherein the pH of the mix isadjusted to a value from 4.5 to 6.0 by the addition of a pH controlagent.
 16. The method of claim 14, wherein the pH control agent isselected from the group consisting of calcium oxide, calcium hydroxide,sodium hydroxide, potassium hydroxide, anhydrous ammonia, cement kilndust, lime kiln dust, fluidized bed ash, Class C fly ash and Class F flyash, multistage burner fly ash, alum, water treatment sludge, wood ash,and combinations thereof.
 17. The method of claim 1, wherein steam isproduced within the pressure vessel and the temperature of the mixincreases due to an exothermic reaction of the components of the mix,and wherein the steam is subsequently removed to create a drying effecton the mix.
 18. The method of claim 17, wherein the temperature increaseof the mix exceeds 100° C., 121° C., 126° C. or 137° C. and, wherein thepressure increase of the mix exceeds 20, 30 or 38 pounds per squareinch.
 19. The method of claim 1, wherein the retention period is aminimum of one minute, from 5 to 30 minutes, or from 10 to 20 minutes.20. The method of claim 1, wherein the sludge is made pumpable by mixingthe sludge with a force sufficient to make it pumpable or by adding aliquid.
 21. The method of claim 20, wherein the liquid is blowdownacid-water from a scrubber system.
 22. The method of claim 1, whereinstep (a) comprises heating the sludge in a pugmill.
 23. The method ofclaim 22, wherein the sludge is heated by a heated shaft, heated paddleblades, a heated jacketed sleeve surrounding the pugmill, or acombination thereof.
 24. The method of claim 22, wherein the sludge isheated to 80° F., 95° F. or 111° F.
 25. The method of claim 22, furthercomprising the step of adding one or more plant nutrients and one ormore hardening agents to the mix in the mixer or pugmill, wherein theone or more plant nutrients are selected from the group consisting ofurea, ammonium nitrate, ammonium sulfate, monoammonium phosphate,diammonium phosphate, urea ammonium nitrate, liquid urea, potash, ironoxide, soluble iron, chelated iron and combinations thereof; and whereinthe one or more hardening agents are selected from the group consistingof ferric oxides, alum, attapulgite clay, industrial molasses, lignon,ligno sulfonate, urea formaldehyde polymerizer and combinations thereof.26. The method of claim 1, wherein vaporized ammonia is added to thepressure vessel.
 27. The method of claim 1, further comprising the stepof forming the mix into granules or pellets by granulation or extrusion,and subsequently drying the pellets.
 28. The method of claim 27, whereinthe granules or pellets are dried to greater than 90 weight percentsolids, to greater than 98 weight percent solids, or to greater than 99weight percent solids.
 29. The method of claim 27, further comprisingthe step of passing the dried granules or pellets through one or morescreens to separate oversized materials and undersized materials fromproper-sized product.
 30. The method of claim 1, further comprising thesteps of passing the mix through a second mixer or pugmill, forming themix into granules or pellets by granulation or extrusion, drying thegranules or pellets, passing the dried granules or pellets through oneor more screens to separate oversized materials and undersized materialsfrom proper-sized product, and reintroducing the crushed oversizedmaterials to the mix in the second mixer or pugmill.
 31. The method ofclaim 30, further comprising the step of crushing the oversizedmaterials in a crusher or mill.
 32. The method of claim 30, wherein theundersized materials comprise dust.
 33. The method of claim 30, furthercomprising the step of cooling the dried granules or pellets in acooling apparatus, wherein the dried granules or pellets are cooled to140° F. or less, 130° F. or less, or 120° F. or less.
 34. The method ofclaim 33, wherein the cooling apparatus is a fluidized bed, a rotatingdrum.
 35. The method of claim 34, further comprising the step of coatingthe dried granules or pellets with a dedusting or glazing material toreduce abrasion and dust generation, wherein the dedusting material isapplied to the granules or pellets within the cooling apparatus.
 36. Afertilizer manufactured by the method of claim
 1. 37. The fertilizer ofclaim 36 which contains at least 10 wt. percent of nitrogen, at least 12percent nitrogen, or at least 14 percent nitrogen.
 38. The fertilizer ofclaim 36 which has zero or an undetectable amount of viable, harmfulmicroorganisms, and which is non-toxic and safe for handling and safefor proper crop applications.
 39. The fertilizer of claim 36 whichcontains ammonium nitrogen bound to compounds in the mix such that thenitrogen dissolves slowly and migrates slowly through the top 8 inchesof soil.
 40. The method of claim 1 in which the pressure vessel isreplaced by three pressure vessels, each filled successively, to permita continuous batch processing of the fertilizer mix under definedtemperature and atmospheric pressure conditions and retention time. 41.The method of claim 1, further comprising the step of passing the mixthrough a mixer or pugmill that follows the pressure vessel in theprocessing sequence.
 42. The method of claim 41, wherein the mix formedin the pressure vessel is an ammonia melt containing incompleteammoniation with excess acid.
 43. The method of claim 42, wherein themix is treated with ammonia to complete the ammoniation process formingan ammonium salt in a sparger in the mixer or pugmill.
 44. The method ofclaim 43, wherein the ammonia is converted from a liquid to superheatedammonia vapor prior to being introduced into the sparger.
 45. The methodof claim 44, wherein the conversion to superheated ammonia vapor isaccomplished by applying a direct heater to an ammonia delivery line orby applying excess heat recovered by a heat exchanger from elsewhere inthe process to the liquid ammonia.
 46. The method of claim 45, whereinthe ammonia vapor is superheated with the temperature controlled at120-200° F., or at 170-180° F., and a pressure controlled at 90 to 120psig.